use a per-call DecimalFormat in OggAudioParser duration output

[rootvector2]

the static DURATION_FORMAT is shared across the ogg parser singletons but DecimalFormat is not thread-safe, so concurrent parses race on its mutable internal state; create it per call inside extractDuration like MP4Parser already does.

[hiSandog]

Moving DecimalFormat to per-call scope is the right fix for thread safety. One small regression test would make this durable: parse two Ogg inputs concurrently with different duration shapes and assert the emitted metadata is stable across repeated runs. That would catch both shared formatter mutation and any future attempt to reintroduce a static formatter for allocation savings.

[rootvector2]

good call. added OggAudioParserDurationTest that drives extractDuration from 32 threads over a set of rounding-heavy duration shapes and asserts XMPDM.DURATION matches the single-threaded value every time. it stays green now and would fail if a shared static formatter ever came back.